Javapoet: Generate try-catch block

Using 'nextControlFlow' method of MethodSpec Builder, we can generate try-catch exceptions.

 

Example

methodBuilder.beginControlFlow("try")
      .addStatement("int i = 10 / 0")
      .nextControlFlow("catch($T e)", ArithmeticException.class)
      .addStatement("System.out.println(\"Error occuured\")")
      .addStatement("e.printStackTrace()")
      .nextControlFlow("catch($T e)", Exception.class)
      .addStatement("System.out.println(\"Error occuured\")")
      .addStatement("e.printStackTrace()")
      .nextControlFlow("finally")
      .addStatement("System.out.println(\"I am in finally block\")")
      .endControlFlow()
      .build();

 

Above snippet generates below code.

  try {
    int i = 10 / 0;
  } catch(ArithmeticException e) {
    System.out.println("Error occuured");
    e.printStackTrace();
  } catch(Exception e) {
    System.out.println("Error occuured");
    e.printStackTrace();
  } finally {
    System.out.println("I am in finally block");
  }

 

Find the below working application.

 

TryCatchFinallyDemo.java

 

package com.sample.app;

import java.io.IOException;

import javax.lang.model.element.Modifier;

import com.squareup.javapoet.JavaFile;
import com.squareup.javapoet.MethodSpec;
import com.squareup.javapoet.TypeSpec;

public class TryCatchFinallyDemo {

  public static void main(String args[]) throws IOException {

    MethodSpec.Builder methodBuilder = MethodSpec.methodBuilder("main");
    methodBuilder.addModifiers(Modifier.PUBLIC, Modifier.STATIC);
    methodBuilder.returns(void.class);
    methodBuilder.addParameter(String[].class, "args");
    
    methodBuilder.addCode("\n");
    
    methodBuilder.beginControlFlow("try")
          .addStatement("int i = 10 / 0")
          .nextControlFlow("catch($T e)", ArithmeticException.class)
          .addStatement("System.out.println(\"Error occuured\")")
          .addStatement("e.printStackTrace()")
          .nextControlFlow("catch($T e)", Exception.class)
          .addStatement("System.out.println(\"Error occuured\")")
          .addStatement("e.printStackTrace()")
          .nextControlFlow("finally")
          .addStatement("System.out.println(\"I am in finally block\")")
          .endControlFlow()
          .build();

    MethodSpec mainMethod = methodBuilder.build();

    String className = "Test";
    TypeSpec.Builder classBuilder = TypeSpec.classBuilder(className);
    classBuilder.addModifiers(Modifier.PUBLIC, Modifier.FINAL);
    classBuilder.addMethod(mainMethod);
    TypeSpec helloWorldTypeSpec = classBuilder.build();

    String packageName = "com.sample.app";
    JavaFile javaFile = JavaFile.builder(packageName, helloWorldTypeSpec).build();

    javaFile.writeTo(System.out);
  }

}

Generated code

package com.sample.app;

import java.lang.ArithmeticException;
import java.lang.Exception;
import java.lang.String;

public final class Test {
  public static void main(String[] args) {

    try {
      int i = 10 / 0;
    } catch(ArithmeticException e) {
      System.out.println("Error occuured");
      e.printStackTrace();
    } catch(Exception e) {
      System.out.println("Error occuured");
      e.printStackTrace();
    } finally {
      System.out.println("I am in finally block");
    }
  }
}

 

 

 

 

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